Retired peer with line that's comical (5)
I believe the answer is:
droll
'comical' is the definition.
(thesaurus)
'retired peer with line' is the wordplay.
'retired' says the letters should be written in reverse.
'peer' becomes 'lord' (I've seen this before).
'with' means one lot of letters go next to another.
'line' becomes 'l'.
'lord' reversed gives 'drol'.
'drol'+'l'='DROLL'
'that's' acts as a link.
(Other definitions for droll that I've seen before include "amusing, in a strange way" , "Whimsical - amusing" , "Zany" , "Large amount (of matter)" , "Funny" .)